Pre-delay is the time between the end of the initial source sound and the beginning of the first reflections (sound returning to your ears after bouncing off the closest surfaces) being audible.

Imagine you’re back on that stage in a large music hall. This time you stand on the very edge of the stage and shout “Hello world!” toward the center of the hall. There will be a brief pause before you hear the first noticeable reflections of your voice, because the sound waves can travel much further before encountering a surface and bouncing back. (There are closer surfaces, of course—notably the floor and the ceiling just in front of the stage—but only a small part of the direct sound will go there, so those reflections will be much less noticeable.)

Adjusting the pre-delay parameter on a reverb allows you to change the apparent size of the room without having to change the overall decay time. This will give your mix a little more transparency by leaving some space between the original sound and its reverb.

Another important factor in getting a great reverb sound is the pre-delay setting. Pre-delay is the amount of time before the onset of the reverberant field. Longer pre-delay settings will add more depth to the reverb when the dry signal is up front in the mix. Shorter pre-delay settings will attach the “wet” reverb to the dry signal more closely, with the wet/dry balance determining how distant the original, dry sound will appear to be.

A good guideline for setting pre-delay times is to match them to the size of the space you are setting up. Think 0–10 ms for smaller size spaces like an average-sized bedroom, 10–20 ms for medium-sized spaces, and over 20 ms for larger spaces like halls and churches.

Keep in mind that these ranges are relative to the tempo, pace and density of the production, so it is usually best to adjust pre-delay in the context of the whole mix rather than in solo.

The first parameters most people tend to adjust when setting a reverb are size or dry/wet. size determines the boundaries of the space in which the reverb will exist but the perception of size actually comes mostly from the timing of early reflections. 

Early reflections are the first set of delays that come directly from the floor, ceiling and walls. Their timing and frequency response send the necessary binaural cues that allow the listener to recognize a dimensional space. These early reflections tend are usually quite distinguishable as opposed to late reflections which is made up of a much more diffused set of reflections that make up the reverbs decay.

The best way to set the size of a space is to begin by adjusting the reverb’s mix control so that you only hear the early reflections, this is very straight-forward to do on Ableton Lives reverb device which has a dedicated mix control for both early and late reflections.

Now you can listen carefully to the defining part of the reverb, the early reflections. Once you have set these you can then add pre-delay to separate the original sound from the reverb.

in terms of acoustic space, adding pre-delay has the same effect as distancing the original sound source from the closest reflective surfaces (which usually defines a bigger space but could also give clues to the listener’s position in a space.

For example, a sound with almost no pre-delay, and a set of early reflections that have a first set of tight reflections, and another set of loose reflections a few milliseconds later would indicate a large room with a listener stood right in the corner, whereas a sound with a big pre-delay and all the early reflections sounding at a similar time would indicate a large room with the listener stood directly in the middle.

Now that we have the pre-delay and size set, we can adjust the mix and adjust our late reflections, which gives us a secondary indication on the type, density, surfaces and size of the room.

Understanding Pre-delay, decay time & RT60

When we calculate RT60 we need to remember that this is the total time taken in milliseconds for the reverb to reach -60dBs. 

Because real reverb is subjective to the acoustic space it is heard in, reverb times and characteristics change depending on:

• The frequency content of the sound source
• The room size
• The original sounds location in the space
• The listening position

This means that an RT60 also includes any pre-delay. So when we are calculating an RT60, we cannot just take this number and use it as our ‘reverb decay’ parameter in Ableton Live and then go and set the pre-delay to whatever we want. Instead, we should be choosing a sensible pre-delay value which matches the sonic environment we are trying to create.

Once we have chosen a pre-delay value, we then subtract this pre-delay value from the RT60.  This will give us our decay time value. Together these two values give us our total reverb time (RT60) which, if synced up using our reverb delay calculator, will be nicely synced to your project tempo. Just remember to also fine tune these values as you see fit to account for the groove & subjective material that you are applying reverb To.

Dry Vs. Wet Reverbs

Choosing The Right Type

Within the vast majority of professional mixes you will usually find a mixture of different reverb configurations and types. Often, these reverbs have been set-up for specific purposes, or specific instruments or groups. I.E – ‘Drum Room Reverb’,  ‘Wide Synth Verb’, or ‘Snare Tone/Body Verb’.

We can break our reverbs up into a number of different ways, but generally speaking, we have our ‘overt’ and ‘covert’ reverbs. Overt reverb is the obvious reverb we want to hear in the mix, and covert reverb is our very subtle, subconscious reverb that serves a purpose whilst being almost inaudible. These could also be referred to as our ‘dry’ reverbs, and ‘wet’ reverbs. 
 

Dry Reverbs are Shorter reverbs such as small rooms & tight ambient spaces. They serve purposes such as creating presence, clarity, separation between sounds, a sense of realism and very subtle but crucially important depth. They do this without audibly washing over the mix and are generally mixed at such a level that you don’t notice them when they are there, but you should notice the absence of them if you were to mute the reverb or the reverbs return track.

These reverbs are vital for the life of your mix and will usually be between 200ms – 800ms (tempo dependant).

Wet reverbs are Chambers, Halls, plates and other long reverbs with a lot more power and depth.  These will play a big part in the feel and tonality in the main parts of your track such as any lead instruments and vocals. The values used for these reverbs still give a strong indication of the size and character of your acoustic space, but these reverbs are here to be heard.

Be careful with the low-end frequency content and length of these reverbs, because they can very quickly wash out a track with muddy low/mid frequencies which will not only cloud the mix but will also kill off the rhythm and groove you have worked hard to create.

Getting the balance between dry & wet reverbs is not easy and takes time to understand. Not all your sounds should be drenched in reverb and not all your sounds should be treated with more than one reverb (however it is fine to do this to some sounds). Remember that the goal here is to create an acoustic space that the listener can picture using just their ears. We can understand that a distant sound is far away if we have a very up-close and present sound to compare it to. This means that we should have a good combination of dry and wet sounds in our mix, using dry and wet reverbs and varying dry/wet levels to achieve that mental picture we are trying to paint.

We can also use reverb devices as inserts on certain sounds which will allow us to slowly reduce the original source sound as we push up the dry/wet value. This can be a great way to really push sounds far into the distant background to help create a soundscape to build upon with up-front sounds.

Inserting a reverb plugin directly to an audio track is the quickest way to add a reverb effect, but greatly limits your ability to process the source audio and reverb effect independently.

A send/return configuration is when we send a duplicated portion of our source audio to a completely new audio track known as a ‘return’ or ‘aux’. We can then affect this return track with completely wet (set to 100% wet) reverb, which we can then mix into the track. 

This opens up our options for processing and automation, and also means we still have the complete original signal in the mix as well as this 100% wet one. In some cases we may actually prefer to use a reverb as an insert effect as it allows us to easily dial in a reverb dry/wet setting that pushes the original sound into the distance (by reducing the ratio between the original and reverberated sound).

This technique works great for lost of different purposes such as distant tech house shakers to help fill out a mix, to atmospheric techno pads. The trick here is to make a firm decision when you add another sound or element to the mix, what role is this element going to play, an upfront sound, or a background element?